High altitude starting two-stage fuel injection apparatus

Abstract

Difficulties in achieving reliable starts in gas turbine engines operating at high altitude are avoided in a gas turbine engine including a rotary compressor (10), a rotary turbine wheel (12) coupled to the compressor (10) to drive the same, and a nozzle (42) for directing gases of combustion against the turbine wheel (12). An annular combustor (34) has an outlet (40) connected to the nozzle (42) and an opposed dome (38) that is axially spaced from the outlet (40). At least three sets of air injection openings (80, 92, 100) are axially spaced from one another with one set (82) in close proximity to the dome (38). Fuel injectors (86, 94) are associated with two of the sets (80, 92, 100), including the one set (80) and another of the sets (92) that is nearest the one set (80). The air injection openings of the sets (80 and 92) and the fuel injectors (86, 94) are constructed, arranged and sized so that the air/fuel ratio of air injected by each of the sets (80, 92) is no more than about 5/1 and the remaining set of air injection openings (100) is constructed, arranged and sized so that the total air/fuel ratio of air and fuel through all of the sets (80, 92, 100) and fuel injectors (86, 94) is approximately stoichiometric.

We claim: 
     
       1. A gas turbine engine comprising: a rotary compressor;   a rotary turbine wheel coupled to said compressor to drive the same;   a nozzle for directing gases of combustion against said turbine wheel;   an annular combustor having an outlet connected to said nozzle and an opposed dome axially spaced from said outlet;   at least three sets of air injector openings, each set axially spaced from one another with one set in close proximity to said dome;   fuel injectors associated with two of said sets including said one set and the other of said sets that is nearest said one set;   said air injection openings of said one and said another sets and said fuel injectors being constructed, arranged and sized so that the air/fuel ratio of air and fuel injected by each of said one and said another sets is no more than about 5/1;   the remaining one of said sets of air injection openings being constructed, arranged and sized so that the total air/fuel ratio of air and fuel through all of said sets and fuel injectors is approximately stoichiometric.   
     
     
       2. The gas turbine engine of claim 1 wherein said openings are tangentially oriented with respect to said combustor. 
     
     
       3. The gas turbine engine of claims 2 wherein said air injection openings are defined by air blast tubes mounted in a radially outer wall of said annular combustor. 
     
     
       4. The gas turbine engine of claim 3 wherein said fuel injectors are mounted in some, but not all of said air blast tubes of said one and said another sets. 
     
     
       5. The gas turbine engine of claim 1 wherein at least some of said openings are defined by perforations in at least one wall of said annular combustor to additionally provide for film cooling of said at least one wall.